1. Field of the Invention
This invention relates to an improved rotary drill and particularly to a drill head assembly for a rotary drill in which a seal arrangement is provided for increasing the life of the bearings and the bearings are supported in a manner to reduce bearing wear and increase the operating efficiency of the rotary drill.
2. Description of the Prior Art
In rock drilling operations, it is the conventionally known practice to drill holes in a rock formation by a rotary drill assembly or by a rotary percussion drill assembly. U.S. Pat. Nos. 3,547,206 and 3,654,961 are examples of such drill assemblies which includes a drill pot that carries a hydraulic motor having a motor shaft nonrotatably connected to a bevel gear which meshes with another bevel gear rotatably journaled on a support member or hub within the drill pot housing. The hub is fixed to a rotatable head or pot cover and has a seat into which the shank of a drill steel is received. A drill bit is positioned on the upper end of the drill steel. With this arrangement rotation of the motor shaft is transmitted to the drill steel to rotate the drill bit.
Generally, the drill assembly is incorporated with a self-propelled machine that maneuvers the drill pot into position and moves the drill pot in the axial direction of advancement of the drill bit into the rock formation. For rock drilling operations in an underground mine the drill assembly is supported by a boom that is pivotally mounted on the front of a mobile frame. Upward pivotal movement of the boom moves a drill steel seated in the pot cover into drilling position. As the drill steel rotates, the boom exerts upward pressure upon the drilling assembly to increase the driving thrust upon the drill steel. This advances the drill steel vertically into the rock formation as rock material is dislodged to form an elongated bore in the rock formation. The upward force exerted upon the drill assembly by the boom overcomes the resistance encountered by the rock structure to rotation of the drill bit. An example of such a drilling machine is disclosed in U.S. Pat. No. 3,190,369.
As the drill bit advances into the rock formation by the upward thrust applied by the drill boom, the resistive forces encountered exert tremendous lateral forces on the drill steel. The lateral thrust forces are transmitted through the drill steel to the drill retaining member and to the bearings which rotatably support the drill retaining member. The effect of the lateral thrust forces is to displace the bearing carriers so that the bearings are no longer maintained in axial alignment in the drill pot. This results in wear of the bearings requiring that the drill assembly be removed from operation for repair of the worn bearings. In addition misalignment of the bearings destroys the seals around the bearings permitting lubricant to escape from the bearings and the entrance of dust and other foreign matter into the drill assembly. Consequently, drilling efficiency is substantially reduced and repair costs substantially increased.
Therefore, there is need in a rock drilling assembly for a drill head capable of withstanding the forces applied thereto during the drilling operations so as to extend the life of the bearings and maintain the drill head sealed against the entrance of foreign material.